Ridding an ecosystem of invasive plants is never easy. We can bring in goats to munch on offending plants or force armies of schoolchildren into slavery to pull them out; but, in all likelihood the sneaky little devils (the invasive plants, not the schoolkids) will be re-sprouting and back with a vengeance before we can turn around. For many invasive plant infestations the most practical long-term solution is chemical control – in other words, herbicides. Of course, herbicides have their issues such as drift and potential impacts on non-target plants. And what do you do when you want to get rid of invasive plants in a remote, sensitive ecosystem with limited access? Enter Herbicide Ballistic Technology (HBT). The HBT system uses the same technology as a recreational paint-ball gun but instead of filling the projectiles with paint, the balls are filled with triclopyr, which is commonly used in homeowner products for brush and poison ivy control.
Dr. James Leary at the University of Hawaii has been exploring the use of HBT to control invasive plants in various ecosystems in Hawaii. Most of the time Dr. Leary and his colleague use the standard paintball HBT system, but for the big jobs they call in the heavy artillery – literally. Dr. Leary recently presented a seminar here at MSU on work he and his team have conducted in conjunction with the Maui Invasive Species commission to eliminate populations of Miconia calvacens, one of the most problematic invasive trees in Hawaii. According to the seminar abstract, Dr. Leary reports “Our best utility for HBT deployment on a Hughes 500D helicopter platform featuring real-time capabilities in target elimination. …we have conducted 17 tactical search and destroy mission covering a total net area of 3,888 ha and eliminating 7,463 Miconia targets.”
Clearly the war on invasive has been raised to a different level
As I mentioned in the last post I was in Austria this past week for the International Christmas Tree Research and Extension conference. We hold these meetings every two years for Christmas tree researchers in Europe and North America to get together and share the latest research on various aspects of Christmas tree production and marketing. In addition to research presentations the programs also include tours of local Christmas tree farms, which is always the most interesting part of the conference.
In Austria one of our tour stops was an organic Christmas tree farm operated by Regina and Michael Spenger. For the most part, my views on organic systems are in line with those that Jeff Gilman has voiced here on the GP blog. There are certainly benefits in reducing pesticide use but it’s not a given that an organic approach is always superior to a conventional system. Nevertheless one hallmark of organic production is that growers must be creative and often develop innovative approaches to production issues. This is especially true when it comes to weed control; one of the most difficult challenges of organic growing. Good weed control is essential in Christmas tree production since grasses and broadleaved weeds are aggressive competitors for water, nutrients and light. To control weeds without herbicides the Spenger’s settled on a novel idea: Sheep. Each morning they release a herd of 40 Shropshire sheep into a plantation and let them munch away. The sheep are allowed to graze for a week and then rotated into another field. Shropshires are well suited to the job since they graze readily on the grass and forbs but leave the trees alone. The Spenger’s also get some small additional returns by selling a few lambs each spring as well as some wool. Obviously this approach has limitations but it certainly highlights important aspect of the organic movement that can benefit all production systems: looking at problems in a different way and thinking creatively.
The sheep herd heading out to a plantation to start their day’s work…
To say that sheep grazing in an Austrian plantation creates an idyllic scene is an understatement.
I am just about the laziest gardener you’d ever want to meet. Around my field plots at the school things tend to look good –but that’s part of my job. Around my home, well, I probably water my plants once or twice a year, I fertilize every few years. I almost never use herbicides or any other weed control methods besides pulling – again, that happens once or twice a year. And I only mulch about once every two years or so (sorry Linda!). My yard does end up being a great place for my experiments on slugs, weeds, and odd methods of insect control, but it’s far from the pride of the neighborhood. Generally I plant things and let them either live or fail and just don’t worry about it that much if they can’t make it. That said, I think that I would fare better if I just accepted weeds as an integral part of my yard. It has already happened in my lawn. This year the clover has finally started to take hold. I’m happy about this because it will mean less fertilizer. In the back yard I’ve knocked out most of the thistle (hand pulling and a little bit of Round-Up), and now daisies are popping up. Sometimes they’re in spots where I’d prefer to have a lilac or rose – but hey, they’re not bad. It almost looks like I planted them on purpose.
My laziness recently however, reached a new level (my wife isn’t particularly pleased about it, but so far the summer has been busy enough that I’ve been able to find lots of excuses). On our back porch we usually grow some tomatoes or cabbage, or something in a container. This year we didn’t bother and so the container started to grow weeds. Specifically purslane. At first this seemed like a bad thing, but then it started looking … good. It filled out the container. It didn’t need any watering, and, by golly, it actually tasted good! Now tasting random weeds from your backyard (or uncared for container) is not something that I encourage. And even if you want to taste purslane have an expert (such as a botanist) confirm that it’s purslane before you go chomping on it. But that said, I tasted this stuff after I found out it was edible and now we have a new leafy veggie for our salads. Then I started figuring out all of the weeds in the yard, both front and back, that are edible. I already love clover flowers and I’m OK with young dandelion leaves. Shoot. I’m starting to think that if I could take my laziness to yet another level my family and I could eat salad all year without ever buying lettuce at the supermarket.
As many GP readers know I’m originally from Olympia, WA. Once a week or so I troll through the on-line version of my hometown newspaper, the Daily Olympian (“the Daily ‘O’” for short or, more commonly, “the Daily Zero”) to keep up with latest happenings back home and to see if any of my high school classmates are on their way to jail. While none of the Olympia High Class of ’78 made the news recently, my interest was piqued the other day by the headline “Saving the world – from weeds”. The article described the Earth day efforts of local grade-schoolers to eradicate Scotch broom from a local nature trail.
For those that are not familiar, Scotch broom is an exotic shrub that commonly invades disturbed areas throughout the Northwest. It’s been a problem for years and, even as a kid 40 years ago, I remember every cutbank around town covered with the nasty yellow blossoms. In doing a little trolling on the internet I was surprised (stunned is probably a better word) to learn that there are parts of the country where Scotch broom is still sold as an ornamental shrub – named cultivars and all. There are commercial cultivars of dandelion after all, so why not?
As we’ve noted here on the GP blog, there are lots of layers of complexity to the native/non-native discussion. In many cases I think native advocates have over-sold the ecological side to the argument. But the Daily O article got my dander up; not because 4th graders were pulling up Scotch broom – good riddance and keep up the good work kids – but because the Scotch broom was replaced with trees and shrubs that were all exotics in that part of the Northwest.
Native plant advocates often downplay the ‘sense of place’ argument in promoting natives. I suppose they feel the ecological arguments are based on ‘harder science’ and therefore more convincing. While it can be argued that native plants have adapted to the environment in which they evolved; it’s not always a given that the native conditions still exists, particularly in the built environment. What’s beyond argument, however, is that trees and other plants provide a connection to the natural world around us and, for lack of a better term, do give us a sense of place. From my personal experience, I have a visceral reaction to the sight of Scotch broom or English ivy in the Northwest where I’m native. Here in Michigan, on the other hand, I’m less bothered by exotics – even some that may be considered invasive. I suspect many native-born Michiganders have the opposite reaction.
I’m sure part of my connection to all things Washington stems from lessons learned in school (I still know all the lyrics to ‘Washington my Home’ and my plant collection form Mr. Chance’s high school Botany class is still somewhere in the attic of my parent’s house). Which is why I was flummoxed by the schoolkids planting tulip poplars and sequoias instead of big leaf maples and western redcedars. Wouldn’t this exercise have been a great opportunity to teach these young people about the great trees and shrubs that are native to the Northwest and to give these kids a sense of place?
A few weeks ago I was in Olympia (it misses you Bert!) reviewing grant applications. As I tend to do whenever I have time and my camera, I set out in search of gardening goofs that evening. Here’s the edge of a relatively new commercial site I discovered:
OK, not too bad so far. We’ve got a nice stone mulch next to the curb, then a lovely groundcover, in flower, that also functions as a living mulch. But what’s that we see in the upper half of the photo?
Yes, it’s Canada thistle (Cirsium arvense), an aggressive perennial weed that spreads by stolons and can make dense monocultures of prickly nastiness. In fact, the front is already advancing on our little groundcover:
Had the landscapers continued with mulching the soil rather than leaving it bare, these thistle seeds might not have germinated. But for whatever reason, the bulk of the landscape was left bare:
I’m sorry, but this just looks ridiculous. There was some obvious care in laying the stone mulch and groundcover, but then the landscaper seems to have run out of time and/or money and just plopped in some bulbs and corms. It reminds me of a birthday cake.
I don’t understand the rationale behind this. Was this a real design? Did the client run out of money? Or (as the more cynical side of me wonders) was this done deliberately to create a high maintenance landscape requiring lots of weeding in the future?
It was fun to read all of your comments last week about your opinions on lawn care. To follow up on it I’m going to talk a little bit about why I’m not fond of companies which apply herbicides multiple times throughout the year. But first I think I’ll mention why I apply herbicides at all — aesthetics. That’s it — the whole reason. Could I go the no-lawn route? Yes, but I like having a yard to run in. Not a huge yard, but a little yard to play tag with the kids.
What I long for though is the yard from the house that I grew up in. Our house in southeastern PA (About an hour west of Philly and an hour east of Lancaster) was set back about 800 feet from the road and was on old agricultural land. The area around the house was planted in grass in the mid 70s and then it was left alone. Fertilized once the first year I think, but that’s it. Dandelions invaded quickly as did clover. Over the years the clover began to dominate the grass, but not to the point that the grass disappeared, and the lawn actually appeared relatively homogeneous. Dandelions never left, but their numbers declined. The clover grew low and the grass never shot up like it does in a heavily fertilized lawn and so mowings only happened once every two weeks or so (well, OK, sometimes more often depending on the weather and where on the lawn you were — the spot over the septic tank needed mowing every 48 hours or so). The grass did go dormant most summers, but 800 feet from the road there wasn’t anyone to complain, and besides, the clover kept the lawn from appearing completely scorched. The lawn looked good for well over 30 years (until my parents remodeled the house and the yard was torn up).
The typical suburbanite might not have liked this lawn, but to me this lawn looked great, and, besides, it was low maintenance. The reason I’m bothering to tell you about this lawn though is because it illustrates so well what lawn care companies make impossible. They say (and by “they” I mean professors like myself) that pesticides beget pesticides and fertilizers beget fertilizers, and nowhere is that as true as in a well manicured lawn. The herbicide of choice is 2,4 D (though there are many others that are used) which lawn care companies apply multiple times over the the course of a year. This pesticide does a great job of killing dandelions, but it also kills clover. It rarely hurts grass unless it’s grossly over-applied. The problem with killing clover is that this clover is the stuff that fed the grass in the house where I grew up. Clover takes nitrogen out of the air and makes it available to grass every time the lawn is mowed (the clipped off pieces of clover degrade and the nitrogen in them feeds whatever plants are around). Without the clover you need to add fertilizers. So, because the lawn care company is keeping the lawn free of weeds they also need to fertilize because they’re killing all of the natural fertilizer. Here’s the thing, the weed that most people in the suburbs like least, dandelions, is actually very sensitive to low potassium. The lower the potassium in the soil the worse it does. In fact, dandelions can easily be out-competed by grass and clover if potassium is low — just as happened in the yard of the house where I grew up. But do lawn care companies pay attention to this (by using high nitrogen, low potassium fertilizers?) What do you think?
My guess is that many of you thought that I’d cite all kinds of scary side effects of the pesticides used on lawns. Nope. In general I think that, if used properly, they’re pretty safe for humans (with a few notable exceptions). I’ve spent a lot of time reviewing epidemiological and toxicology studies and I can think of many worse things. I am somewhat fearful of what 2,4 D may do to dogs in particular — they can’t excrete this poison like we can. Don’t think for a minute that I’m calling these poisons perfectly safe — I just think there are plenty of other better established reasons to avoid lawn care company pesticide schedules.
Yesterday evening I took my older daughter to dance class while my wife stayed home. While she was entertaining our younger daughter, the TruGreen guy came to the door to tell us that we had weeds in the yard (Damn, I had no idea!). He went on to tell my wife that we really needed to use his company to get rid of them. I was so disappointed that I missed him because I wanted to know all about what he had planned for our yard. Many of our neighbors use TruGreen and I have to say that I’m not particularly impressed. It’s not that they’re not professional — they certainly are. It’s not that they don’t do things by the book — they certainly do. It’s just that the book that we use is getting a bit outdated. When I read TruGreens online FAQ it looked like they actually plan six applications of chemicals per year. I’m assuming (I don’t know this for sure), that at least four of those include herbicides to one extent or another. It looks like people who have no tolerance for weeds should love TruGreen. But really, how many weeds should people allow in their yards? Is it one per square foot? Two? Five dozen? And what are weeds? Is clover a weed? At what point do we say enough is enough and that we’d rather just cope with a few weeds than hose down our whole yard with herbicides.
After reading my own words I feel like some kind of radical. In my job I tend to see two types of people, those who can’t stand pesticides and those who can’t stand weeds. One group is happy to spray five times a year if it means that their lawn will be weed free, and one won’t touch an herbicide. I’m not sure that either group is correct. I tend to handle weeds in my yard the same way I handle haircuts – I hate having my hair cut so I don’t go to the barber that often, but I do go to the barber eventually because my hair looks pretty ridiculous if it grows too long. I feel the same way about weeds (specifically dandelions) which infest the grass in my yard. I prefer not to add herbicides, but there’s a big weed bank in the area and so I end up needing to apply once every two years or so because otherwise it looks pretty bad. Rather than making either the making the weed-free lawn or the no-chemical group happy though I think that it just pisses them both off. They see my unwillingness to commit to one way or the other as a cop-out rather than reasonable moderation. What do you think?
As Austrian reader Johannes explained, the difference in dandelion flower height is due to herbivory – in this case from a lawnmower. Dandelions are quite adaptable to variable environments (the phenotypic plasticity Johannes also mentioned) and flower heights will increase or decrease depending on these variables. This ensures that the flowers will be accessible to pollinators, yet not decapitated by lawnmowers. It’s just one of the fascinating traits that make weeds successful!